1. Field of the Invention
The present general inventive concept relates to a developing apparatus and an image forming apparatus having the same, and to a developing apparatus and an image forming apparatus having the same, which clean a developer which has not been transferred on a photosensitive medium using a compact developing cartridge
2. Description of the Related Art
In general, an electrophotographic image forming apparatus such as a laser printer, a facsimile, a digital copy machine, etc., scans a light onto a photosensitive medium charged to have a predetermined electric potential to form an electrostatic latent image, develops the latent image with a predetermined colored toner, and transfers and fuses the developed image to a printing medium to print the image.
FIG. 1 is a schematic sectional view illustrating a conventional electrophotographic image forming apparatus.
Referring to FIG. 1, the electrophotographic image forming apparatus includes a cabinet 10, a charging unit 11 provided inside the cabinet 10, a photosensitive medium 13, a light scanning unit 15, a developing cartridge 20, a transferring roller 17 and a fusing roller 19.
The photosensitive medium 13 is disposed inside the developing cartridge 20. The photosensitive medium 13 is charged to have a predetermined electric potential by the charging unit 11, and responds a light L1 scanned from the light scanning unit 15 to form an electrostatic latent image corresponding to an image to be printed.
The developing cartridge 20 accommodates a developer T1 in a developer accommodating part 25, and supplies the developer T1 to the photosensitive medium 13 through an agitator 27, a supplying roller 24 and a developing roller 21 to form the image. Here, a regulating blade 23 is applied to an outer surface of the developing roller 21 to regulate the amount of the supplied developer T1. The developer T1 transported through the developing roller 21 passes between the regulating blade 23 and the developing roller 21 to form a developer layer having a predetermined thickness on the developing roller 21.
The image formed on the photosensitive medium 13 is transferred to a print medium M1 transported between the photosensitive medium 13 and the transferring roller 17, and is fused to the print medium M1 by the fusing roller 19.
A cleaner 30 removing a foreign substance such as a waste developer W1 remaining after developing, etc., and a waste developer accommodating part 29 accommodating the foreign substance W1 removed by the cleaner 30 are provided inside the developer cartridge 20.
The cleaner 30 includes a cleaning blade 31, an end part of which forcedly contacts an outer surface of the photosensitive medium 13, and a bracket 35 coupling the cleaning blade 31 to the developing cartridge 20. Here, the cleaning blade 31 is formed of material having a predetermined elasticity such as urethane, etc., and is adhered to the bracket 35. Accordingly, the cleaning blade 31 contacts the photosensitive medium 13 with a predetermined pressure to remove developer T1 which has not been transferred and remains on the photosensitive medium 13 and other foreign substances.
In configuring the image forming apparatus, it is preferable to reduce the total size thereof. To assist this goal, the volume of the developing cartridge 20 may be reduced.
To reduce the size of the developing cartridge 20, it is helpful to reduce the diameter of the photosensitive medium 13 and to dispose the components in a more compact configuration.
The conventional cleaner 30 is disposed inside the developing cartridge 20 such that the cleaning blade 31 and the bracket 35 are disposed in a height direction of the developing cartridge 20. Also, because a free length 31 a of the cleaning blade 31 is long, and the height of the bracket 35 is high, there is a limit in in the ability to reduce the height of the developing cartridge 20.
Specifically, the cleaning blade 31 is generally formed of urethane, and a line pressure between the cleaning blade 31 and the photosensitive medium 13 is required to be approximately 15 g/cm2 to 35 g/cm2. To satisfy this, it is necessary to appropriately size the free length 31a. If the free length 31a is short, the line pressure increases. Accordingly, a driving torque of the photosensitive medium 13 increases, and the surface of the photosensitive medium 13 is abraded. Accordingly, because the free length 31a in the conventional cleaner 30 should not be shortened to be smaller than 4 mm, the reduction in the height of the developing cartridge 20 becomes problematic.
Also, in the conventional developing cartridge 20, the line pressure of the cleaning blade 31 depends on the free length 31a and a coupling position to the bracket 35. Accordingly, it is difficult to adjust the line pressure to a value within a predetermined range.